Optical absorption at its onset in sputter deposited hafnia-titania nanolaminates

Journal Article · Wed Dec 15 00:00:00 EST 2010 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.3520678· OSTI ID:21537983

Cisneros-Morales, Massiel Cristina; Aita, Carolyn Rubin ^[1]

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1. Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, P.O. Box 413, Milwaukee, Wisconsin 53201 (United States)

The onset of the fundamental optical absorption edge in sputter deposited HfO{sub 2}-TiO{sub 2} nanolaminate films grown on unheated substrates was investigated. Three bilayer architectures were examined, representing overall film chemistry from 0.51 to 0.72 atom fraction Hf. The goal was to determine the absorption coefficient, {alpha}(E), versus incident photon energy, E, and to model this dependence in terms of the absorption behavior of specific functional units within the nanolaminate. Persistence and amalgamation models were applied, representing the extremes of segregated cation and mixed cation structures, respectively, and both were found to be unsatisfactory. Consideration of physiochemical data for the nanolaminates led to the development of a modified persistence model for absorption. {alpha}(E) was decomposed into contributions from (I) broad (9 nm-thick) interfacial regions that were chiefly o-HfTiO{sub 4}, and (II) regions remote from interfaces that contained material based on a highly defective m-HfO{sub 2} lattice. The absorption edge at its onset in all nanolaminates was determined by short-range atomic order characteristic of o-HfTiO{sub 4}. An indirect band gap of E{sub G}=3.25{+-}0.02 eV was determined for this compound.

• OSTI ID: 21537983
• Journal Information: Journal of Applied Physics, Vol. 108, Issue 12; Other Information: DOI: 10.1063/1.3520678; (c) 2010 American Institute of Physics; ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
77 NANOSCIENCE AND NANOTECHNOLOGY
ABSORPTION
ATOMS
CHEMISTRY
COMPOSITE MATERIALS
DEPOSITION
ENERGY GAP
FILMS
HAFNIUM COMPOUNDS
HAFNIUM OXIDES
INTERFACES
LAYERS
NANOSTRUCTURES
PHOTONS
SPUTTERING
SUBSTRATES
TITANATES
TITANIUM OXIDES
BOSONS
CHALCOGENIDES
ELEMENTARY PARTICLES
MASSLESS PARTICLES
MATERIALS
OXIDES
OXYGEN COMPOUNDS
REFRACTORY METAL COMPOUNDS
SORPTION
TITANIUM COMPOUNDS
TRANSITION ELEMENT COMPOUNDS